The broad agreement is the most significant change in the chamber's rules in 35 years.

Majority Leader Harry M. Reid (D-Nev.) and Minority Leader Mitch McConnell (R-Ky.), appearing together on the chamber floor at noon, left intact the minority's right to block some legislation by requiring a 60-vote threshold through a threatened filibuster. But the leaders agreed to repeal the decades-old stalling tactics of secret holds - in which an anonymous senator could slow action on a bill - and the ability to force amendments to be read in their entirety on the floor.

Leaders said they hoped the deal would encourage the free-wheeling bipartisan debates that are part of the chamber's lore but have become increasingly rare as the highly partisan Senate has become bogged down in procedural maneuverings.

"We're going to try to legislate," Reid said in a brief interview after announcing the deal.

Perhaps the most fundamental shift was the agreement to reduce by one-third the number of federal government positions that require Senate confirmation. The current total stands at more than 1,200 slots, from the secretaries of defense and state to the part-time directors of the Broadcasting Board of Governors.

The Senate often has a massive glut of pending nominees. That backlog drew much criticism in early 2009, when Treasury Secretary Timothy F. Geithner worked for months without his top advisers while waiting for the Senate to approve the appointments.

In December, 25 nominees to agencies and boards were left pending, approved by committees but not by the full Senate, and instead were returned to President Obama. The new deal means hundreds of nominees to lower-level posts will no longer have to spend months, sometimes years, going through the confirmation process.

Sens. Charles E. Schumer (D-N.Y.) and Lamar Alexander (R-Tenn.), the Rules Committee leaders who worked out most of the deal, will craft legislation to determine which posts to exempt from confirmation. On Thursday, the pair singled out assistant secretary posts for legislative affairs and communications, as well as part-time board members of commissions, for exemption. Judicial nominations are not affected by the deal.

For Senate insiders, another major concession by McConnell and Reid was an agreement that neither would support a bid to change the way senators vote on the chamber's rules. Traditionally, a rules change requires a two-thirds majority vote. In the past six years, junior senators in both parties have pushed for a simple-majority vote.

Democrats elected in 2006 and 2008, who argue that Republicans have abused filibuster rules, took credit for the changes, the most significant since the filibuster threshold was lowered in 1975 from a two-thirds majority to 60 votes.

Reid and McConnell also made a handshake deal to rein in their use of parliamentary maneuvers. McConnell has agreed to rarely use a tactic that forces Reid to hold a vote to break a filibuster on a motion to consider a bill - one that Republicans used 26 times during the 111th Congress in 2009 and 2010. Reid has agreed that he will rarely maneuver to forbid Republicans to offer amendments, something that had become so common that Republicans said the majority leader has smashed modern records.

Both Reid and McConnell agreed that the fundamental principle of requiring a supermajority - 60 votes - to pass a bill must not be touched.

"Our ability to debate and deliberate without the restraints of time is central and unique to the United States Senate," Reid said. "It's supposed to be that way. It's in our DNA. It's one of the many traits intentionally designed to distinguish this body from the House of Representatives and from every other legislative body in the world."